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Re: R129 SL 72 AMG

There is much confusion about these engines around. Alot of figures are made by wild guessings and assumptions. Fueld by "experts" ...
According to the parts lists of amg, the 72 and 73 have the same bore and stroke. The 7.0 was available as lh and me engine. The 7.2 and later called 7.3 (with the same bore and stroke) only as me. As just written in the German exotenforum, the car there is not a 7.2 it's a 7.0 as written in the documents.

Re: R129 SL 72 AMG

All these data, and some engine stickers like the one in my first post, made me convinced the M120 E70 and the M120 E72 are in fact the same engine. That is, if i stick to the figures. I mean, equal displacement but different kW and Nm.

First there was the E72, then the E70. And last the E73. Which in fact is a M297. And not a M120.

However, some documents and images still refer to M120.983 when the 7,3 engine is meant.
But that must be because the VIN leads to SL 600. And the 7,3 is at some later stage put in.

Confusing stuff. Like what about M120.990? I have seen that in SL 73 AMG car registration. And at the same time M120.983.

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Re: R129 SL 72 AMG

Confusing. Because i still do not know for certain, why the M120 E72 is called E72. Most likely is displacement. Like M120 E70 is 7055 cm3. Seems pretty accurate.

But 7,2 !! Where does that come from?

Maybe it deals in some sort of way with the W202 C 36 AMG. And the M104 E36 engine. The C 36 AMG was the first AMG model when being official Mercedes-Benz partner. The W202 C 36 was the top of the cheapest modelrange at the time. So why not call the top of the most expensive modelrange at the time - W/C140 and R129 - twice that figure? 2 x 36 = 72.

Or is it just my imagination running away with me? Great song. I prefer the Stones version.

Re: R129 SL 72 AMG

To my knowledge, AMG has only ever reported two different V12 R129 cars: (1) the SL 70 AMG at 7055 cubic cm (97.0 x 92.0); and (2) the SL 73 AMG at 7291 cubic cm (80.2 x 92.4). And those are the only two configurations they've ever reported for the M120 engine in any car, R129, C140, or W140 -- and they put them both in each chassis. Although curiously, when they report on the S73 -- "A Bold Giant" as they call it, they show the Displacement and Bore x Stroke as "Unknown." Go figure.

But everywhere else it's consistent -- the 70 designation is a 7055 cubic cm M120, and the 73 designation is a 7291 cubic cm M120.

That same AMG 45 book... I knew you'd check the math, which is why I threw it up there.

But I'm not sure that's the right math. Multiplying two numbers produces a squared number. It takes multiplying three numbers to produce a cubic number. When I walk through AMG 45, multiplying bore x stroke NEVER nets the number they report for cubic displacement.

For example, on the E60 W124 car, they report a bore of 100.0, a stroke of 94.8, and a total displacement of 5956 cm3. And we all know 100 x 94.8 is 9480, not 5956. I think you need some other number. Isn't the bore a diameter number? That doesn't tell you the area of the cylinder circle, just the diameter of it.

So using Area = pi x Diameter can get you the area of the cylinder circle. Multiplying that by the stroke can get you the volume of that cylinder. Multiplying that by the number of cylinders will get you total displacement. I've confirmed that math on the E60 M119 engine -- each cylinder has a volume of roughly 7.44, which multiplied by 8 cylinders (V8) gets you roughly 5,956 cm3. I'd expect that math to hold for the V12s as well.

Re: R129 SL 72 AMG

The often seen 7.2 badge is listed in the 7.3 parts list as well there is a special 7.2 intake manifold cover used for some models delivered to Brunei.

In the 7.0 lh and me are different type of cams installed.
All versions use the same head gaskets.

The differentiation of 7.2 and 7.3 was due to the fact that a 7.3 was officially available in the SL chassis, the 7.2 was the unofficial version available for different chassis such as also w and c 140 before the official sl73 was introduced.

Math aside, it still doesn't make sense that the 73 has such a smaller reported bore than the 70, when the strokes are roughly the same and they both have 12 cylinders. Part of the reason for my confusion on some of this, is the inconsistencies in AMG's own reporting of this stuff.

The 80.2 x 92.4 reported for the SL73 was apparently a typo or just plain wrong. For the CL73 and the CLK GTR 7.3 car, both with 7291 cubic cm, they report 91.5 x 92.4, as GSXR indicates. Which calls me to question the 97.0 x 92.0 they report for the 70 series cars. It just can't be true -- math doesn't lie. Pun intended.

As I look at the way these numbers are reported in the various models, I'd bet the SL70 was a 90.0 x 92.4. That is, the "80.2" was a typo, and reported for the wrong model. There was a second V12 CLK GTR 6.9 car, which had 6898 cubic cm, 89.0 x 92.4. That tells me ALL of the V12s had a 92.4 stroke, and only the bore diameter changed, which makes some business manufacturing sense (same block). The CLK GTR 6.9 had an 89.0 bore; the SL, CL and S 70 cars had a 90.0 bore; and the CLK GTR, SL, CL and S 73 cars had a 91.5 bore.

Are there pistons to support a bore between 90.0 and 91.5 in your "unofficial" parts lists? I think that's the only way you get an AMG V12 72 car. A 91.0 bore would get you 7212 cubic cm.

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Re: R129 SL 72 AMG

I can't solve your puzzle, but engine management could produce different output from the same displacement. AMG has numerous examples of the same engine with different output. When I'm back to the book, I'll provide a couple. I also cannot comment on the papers.

Re: R129 SL 72 AMG

Originally Posted by maw1124

I can't solve your puzzle, but engine management could produce different output from the same displacement. AMG has numerous examples of the same engine with different output. When I'm back to the book, I'll provide a couple.

Yes - different engine management, different camshafts, different head porting, different compression ratios... etc, etc.

The important thing, IMO, is the actual bore & stroke numbers. There seem to be an awful lot of different numbers which seems odd to me. The M119 only has 2 crankshafts available (MB 94.8, and Brabus 100, AFAIK) and the bore varied from 100-102mm depending on the tuner. Were there really that many custom cranks produced for the M120?

90.4
91.0
92.0
92.4
95.0

I think MAW is on to something where there were probably only 2 different cranks from AMG, with varying bore diameters. Harder to say what RENNtech or other tuners did. Magazine articles say RENNtech had a "custom billet 95mm crankshaft", which would help solve the mystery, if true.

Re: R129 SL 72 AMG

I think there were only two AMG variants -- 70 and 73. The CLK GTR cars I looked at for reference only, as they were a different block. But I found it not a coincidence that they all used a 92.4 stroke. So I think you only had 2 different bore sizes from them, 90.0 and 91.5. Consistency with the M119 points to an internal policy -- you have to keep some limits on the science projects.

Might they have toyed with a 92 bore and deemed it too risky? Sure. Might someone have taken a 90 bore and fiddled with it? Sure. Might an aftermarket tuner have done something that they could sell but that might fail under pressure? Sure.

But I think only 2 passed MB AMG's tests -- the 70 and the 73. And those tests, the discretion and care and engineering budget they entail, is the only thing worth buying for my money.

And for all we know, what's in the system as a 72 is what was BADGED the 73, just like today's 6.3's are nothing more than a marketer's pipe dream.

Re: R129 SL 72 AMG

That's what I've said further up already. There's the 7.0 an& 7.2/3.
Bore on the 7.0 is 91mm,on the 7.2/3 91.5mm.
Since I had to work on two of these engines I have the complete parts list from AMG with all specific part numbers. The crank of the 7.0 is different in stroke than the 7.2/3. Further are the rods of the 7.2/3 made out of titanium alloy.
7.0s are rated 496hp
7.2/3 are rated 525hp, for the royal family of Brunei was a special version with 565hp made.

To make a correct statement about the installed version it is absolutely mandatory to get the amg engine number stamped in on the side of the block. There you will find also find a clear identification of the engine capacity.

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Re: R129 SL 72 AMG

Funny, below is a quote from the AMG Private Lounge...

"Dear AMG Private Lounge members,

For today’s Throwback Thursday we go back to 1999. Just before the turn of the century, Mercedes-AMG presented the SL 73 AMG, undoubtedly the leader in the small, exclusive segment of open super sports car. With a performance output of 386 kW, the vehicle accelerated from 0 to 100 km/h in just 4.8 seconds.

Even today the AMG 7.3 liter V12 engine continues to impress: a stroke of 80.2 millimeters and a cylinder bore of 92.4 milimeteres delivering a volume of 7,291 cubic centimeters. But despite its emphasis on speed, the SL 73 AMG stunned customers with its litheness and – of course – its typical Mercedes-Benz style sporting AMG styling at the front, sides and rear, plus the 18-inch lightweight alloy AMG wheels.

Let it also be noted that to this very day, the SL was the only vehicle among competitors of its era to be equipped with an automatically extending roll bar that offered open-air driving with optimal safety.

Re: R129 SL 72 AMG

Originally Posted by weide1

Brabus 6.9 = 90 x 90 mm.
Brabus 7.3 = 91 x 93 mm

Some of the cc's are not matching from other sources. I wonder which are correct.

I had seen a Brabus 6.9L as 6,866cc (unknown bore/stroke). The one above shows 6,871 (which matches 90x90 bore/stroke). This may simply be a rounding error; if the value of pi is only 3.14 the maths work out to 6867cc (4cc less than if 3.14159 is used for pi).

For the 7.3... looks like the same thing. Pi at 3.14 = 7255cc, pi at 3.14159 = 7258cc.

Re: R129 SL 72 AMG

Good afternoon Gentlemen,

I'll start by confessing I'm a bit of an imposter. I don't actually own a 500E, though I've been lucky enough to drive and admire one which belonged to a good friend of mine. That car was very recently sold to Rowan Atkinson of Mr Bean fame.

I'm here because I found this thread whilst searching Google for info on the SL73 AMG.

I've just purchased a Sultan of Brunei RHD SL73 AMG with very low miles. The car was sourced in Brunei and is currently on a boat heading toward these shores. It's been sitting unloved for a long time and will need work to get it up and running again.

For weeks now I've been researching these cars and their history. I've never come across a car which has so much conflicting information. The story around the Sultans cars make it all the more complex but also all the more interesting!

Your research regarding the engines is fascinating. Until now everything I've read tells me the SL70 was the 'base' model and the 72 and 73 were effectively the same car with a badge change around 1995.

Does anyone have information relating to how many of these cars were made? I've read a total of 85, of which 35 were SL72 and 50 were SL73. But the info on here re the engines would seem to blow that theory apart.

To confuse matters even more, the Sultan of Brunei cars are sometimes referred to as SL730 and have a more powerful engine fitted (565bhp). Are these included within the numbers above?

The Sultan apparently ordered somewhere between 25 and 52 SL73's/SL730's with the more powerful engine, but I only know of two and another two which are called Argento and have been butchered with nasty Honda concept car bodywork. All of these are RHD.

Personally I don't think the numbers are correct. I believe the confusion comes about as he owned between 25 and 52 Mercedes with that specific engine, not all of which are SL73's. Certainly he ordered ten S Class estates with this engine.

Re: R129 SL 72 AMG

Confusing and conflicting information? Or do more versions exist that i know of?

Up till now i thought a 7055 ccm M120 AMG engine comes in 2 versions. A 7.2 LH version with 386 kW. Called M120 E 72.
And a 7.0 ME version with 365 kW. Called M120 E 70.
Check my posts and images above.

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Re: R129 SL 72 AMG (M120 7-liter engine specs)

In order to provide the number of cars that were made, I am sorry Chris(89speedster). But i do not have such specific information. Numbers of how many were made is also less important to me. I try to get the engine specifications. Is already as hard as it is!

Further, I only have this VIN of a Brunei SL 730. WDB1290762F158532. And some images. Also from when it was offered in the UK.

Conclusion, since you tell you know of 2 Brunei SL 730 versions, it is more likely you provide us - or at least me - of that information. Would be helpful. And appreciated over here.

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Re: R129 SL 72 AMG (M120 7-liter engine specs)

What I can tell you is that the Sultan of Brunei never purchased anything like 50, SL73. He ordered approximately 50 Mercedes Benz with the higher output 565bhp engine, but they were fitted to a variety of models including his S Class Kombi's.

He did buy a lot of standard SL600 though, Perhaps people have assumed these were all converted to SL73 spec.

Actually, only four SOB SL73 are known. Two were butchered and used as the base for his Argento concept, one is in the UK and the other is heading to the UK now. All of these are RHD.

I have been collating chassis numbers (17 so far). The three earliest cars are all four speed 'SL72' and these are the only 72's that appear on the list. There is then a gap of approx. 1 year before the first SL70 was delivered in late 95 and the first SL73 late 96.

An LH engine means the car is an SL72 with a 4 speed box. These are the earliest of the 70/72/73 cars. I'm not sure how AMG named these cars back then. I don't think it was SL72 as there are very few references to this name anywhere, but would be happy to be proved wrong.